Year	% of expense
2001	18.120542405419336
2002	19.855364462448367
2003	20.575454891244576
2004	19.507836502676092
2005	19.43207615244521
2006	20.828546968604332
2007	21.734430533333192
2008	22.904209927964235
2009	21.771293280745883
2010	20.048054815363347
2011	17.290370284426064
2012	19.953385362256498
2013	21.199737925969
2014	21.927562010663646
2015	22.689890903624832
2016	20.254017657474403
2017	19.89372890141949
2018	21.13999417965845
2019	20.51608996048209
2020	22.57103042502129
2021	24.030830960599516